Growth-Competition Relationships in Young Hardwood Stands on Two Contrasting Sites in Southwestern Wisconsin

Abstract

Crown-based competition measures were used to assess the relationships between growth and competition for trees in young mixed-hardwood stands on two ecosystems with contrasting site conditions. The two southwestern Wisconsin ecosystems compared were gently sloping summits with deep loessal soils and steeply sloping southwesterly backslopes with loam soils. Individual trees were sampled from variable-radius plots located in 15 stands of 4 to 42 years old. The two best predictors of height growth are the height of a tree relative to the average height of dominants and codominants, and the cross-sectional area of the exposed portion of the crown at its widest point. The data confirmed theoretical relationships between growth and light intensity for species of differing shade tolerance. However, growth rates as a function of relative height did not approach an asymptote for any species, while growth response to increasing exposed crown area was asymptotic for the tolerant species. Species' relationships differed between the two ecosystems, with maximum height growth rates being lower on the drier site. Acer saccharum was the most efficient species (highest basal area growth rate) at the higher values of exposed crown area, but larger total crown size for sugar maple was a contributing factor in such cases. For. Sci. 36(4):1032-1049.